Linear relay actuator



Sept. 21, 1965 'r. E. LOHR v 3,207,961

LINEAR RELAY ACTUATOR Filed Sept. 25, 1963 I NVEN TOR.

United States Patent 3,207,961 LINEAR RELAY ACTUATOR Thomas E. Lohr, Detroit, Mich., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Sept. 25, 1963, Ser. No. 311,452 5 Claims. (Cl. 317191) This invention relates to solenoid operated relays and, more particularly, to an improvement therein for linearizing the magnetic pull or force exerted by the relay over the entire range of armature displacement.

In a conventional solenoid operated relay employing an armature carrying a ferromagnetic end cap and mounted coaxially with an electrically energizable solenoid, a relatively large air gap exists between the solenoid and the end cap when the apparatus is in the deenergized condition.

Energization of the solenoid causes the armature and end cap assembly to be displaced toward the solenoid, thus, causing the air gap between the solenoid and the end cap to decrease correspondingly. As the air gap decreases, the magnetic force of attraction on the end cap increases with the result being that the conventional solenoid operated relay is capable of exerting a holding force which is many times its starting force. If the solenoid actuated relay is to .be used in circumstances where a strong starting force is required, a relay which is much larger than that required to exert the necessary holding force must be used due to the marked non-linearity of the magnetic pull characteristics over the range of displacement of the armature.

The conventional armature often uses a coil or leaf spring disposed between the end cap and the solenoid frame for the purpose of returning the armature to the initial position for re-use. In accordance with the present invention, the conventional coil or leaf spring is replaced with a plurality of resilient spring members formed from a material exhibiting a low magnetic reluctance characteristic. The spring members are so formed that they may be disposed coaxially with the armature and intermediate the solenoid and the end cap to both act as a return spring and also to provide a substantially unchanging and continuous flux path from the solenoid to the end cap which is not dependent in its flux transmission characteristics upon the axial position of the armature or end cap. The present invention is, thus, effective to eliminate the non-linear magnetic pull characteristics which are common to conventional solenoids and to substantially linearize the pull over the entire range of displacement of the armature.

In a specific embodiment the spring members are formed of resilient material, such as steel, and are given a generally concave shape. In addition, the spring members are so formed as to have substantially flat central and peripheral surfaces which, when the spring members are mounted coaxially with the armature as described above, lie in parallel planes which are normal to the axis of the armature. According to the invention, two or more of the spring members are disposed on the armature and intermediate the end cap and the solenoid such that the sense of concavity of alternate members is opposite, and like surfaces, either central or peripheral of the members, are in mutual contact. In this position large peripheral or central areas of adjacent spring members are in contact to define a substantially continuous flux path from the solenoid to the end cap. Additionally, the spring mem- 'bers act in a bellows fashion to provide a spring action or return force on the armature.

The invention may be more readily comprehended upon reference to the accompanying drawings of which:

FIGURE 1 is a cross-sectional view of a solenoid actuated relay assembly employing a specific form of the present invention;

FIGURE 2 is an enlarged cross-sectional view of the specific spring members shown in the embodiment of FIGURE 1; and

FIGURE 3 is an exploded view of a pair of adjacent spring members as may be used in the solenoid assembly of FIGURE 1.

Referring first to FIGURE 1, there is shown a solenoid operated relay comprising a solenoid coil 10 wound about a cylindrical coil form 12 which may be made of Teflon or similar insulating material and disposed within a steel or iron frame 14. Disposed within the central cylindrical opening of the coil form 12 and adapted to ride therein is a steel armature 16. Riveted to the end of the armature 16 is a steel end cap 18 which, due to its ferromagnetic qualities, is subject to the margnetic field generated by the solenoid 10. As shown, a lead-in wire 20 is provided to connect the solenoid 10 with a source of energizing potential. In addition, a solenoid ground wire 22 is brought out through a mounting plate 24 to which the frame 14 is rigidly attached.

Under normal conditions when the solenoid 10 is energized the armature 1'6 and end cap 18 assembly is drawn to a position within the solenoid 10 wherein the center of mass of the armature assembly coincides with the center of magnetic flux of the coil. It can be seen that as the end cap and armature move to the right as shown in the drawing, the air gap between the end cap 18 and the solenoid frame 14 decreases. This decreasing air gap tends to increase the force of magnetic attraction on the end cap 18 as it moves toward the solenoid 10.

According to the invention, a plurality of spring steel members 26 are disposed on the armature 16 between the end cap 18 and the housing 14. The members 26 may conveniently take the form of specially designed washers. As indicated in FIGURE 1, the washers 26 are symmetrical, of generally concave shape and are disposed coaxially about the armature 16 in what may be termed a bellows fashion, that is, in opposite senses of concavity, to provide a spring return force on the end cap 18 and also to provide a substantially continuous flux path of low reluctance between the solenoid 10 and the end cap 18.

Looking to FIGURES 2 and 3, it can be seen that the spring steel washers 26 are so designed as to be substantially dish-shaped or concave and have substantially flat central surfaces 28 and peripheral surfaces 30. When mounted on the armature 16 as shown in FIGURES 1 and 2, the washers 26 are disposed such that alternate washers are disposed in opposite senses of concavity. In this position the flat annular peripheral surfaces 30 of adjacent washers 26 are in intimate contact as are the annular flat central surfaces 28. As shown in the figures, a number of the washers are provided between the end cap 18 and the solenoid housing to define a substantially continuous flux path over the air gap between the end cap and solenoid. Due to the nature of the flat central and peripheral surfaces 28 and 30 respectively, it can be seen that the flux transmission characteristics of the plurality of washers 26 remains unafiected by the axial position of the end caps, so long, of course, as the mutual contact between adjacent washers is maintained. In addition, due to the bellows action of the spring steel washers 26, a return force is provided. Therefore, the force-displacement characteristic of the relay very closely approximates the linearity of the spring washers 26.

Although the spring washers 26 are shown in FIGURE 3 as being substantially circular, it is apparent that other shapes are equally feasible and in accordance with the present invention. Also, while the washers are described as being constructed of steel, any other material exhibiting the proper resiliency and low magnetic reluctance may be employed. While various modifications may be made to the specific embodiment of the invention shown and described above without departing from the spirit and scope of the invention as defined by the appended claims.

What is claimed is:

1. In combination, electrically operated relay means comprising a solenoid energizable to produce a magnetic field, an armature mounted for displacement along the axis of the solenoid, a cap mounted on an extremity of .the armature and subject to the magnetic field to move relative to the solenoid, and a plurality of dish-shaped spring members of low magnetic reluctance disposed coaxially with and normal to the armature and intermediate the cap and the solenoid, the members being disposed in alternately opposite senses of concavity with substantial portions of adjacent members being in mutual contact thereby to provide a spring force tending to oppose movement of the armature and cap toward the armature.

2. Electrically operated relay means comprising a solenoid energizable to produce a magnetic field, an armature mounted for displacement relative to the field, a ferromagnetic member fixed to the armature and normally displaced a predetermined distance from the solenoid but subject to said magnetic field to move toward the solenoid, first and second resilient members of low magnetic reluctance disposed coaxially with the armature and inter mediate the ferromagnetic member and the solenoid, the resilient members being of concave shape and having formed thereon substantially fiat central and peripheral surfaces mutually parallel and normal to the armature axis, the members being disposed such that the concavities thereof are in opposite senses and with one of said surfaces in mutual contact to define a continuous flux path from the solenoid to the ferromagnetic member.

3. Relay means as defined by claim 2 wherein the resilient members are dish-shaped and the peripheral surfaces thereof are in mutual contact.

4. Relay means as defined by clai-lm 2 wherein the resilient members are dish-shaped and the central surfaces thereof are in mutual contact.

5. Electrically operated relay means comprising a solenoid energizable to produce a magnetic field, an armature mounted coaxially of the solenoid for axial displacement, a ferromagnetic member mounted on the armature, the member being spaced from the solenoid and subject to attraction by the magnetic field, a plurality of dish-shaped members of resilient material having a low magnetic reluctance and being coaxially disposed on the armature intermediate the solenoid and the ferromagnetic member, the resilient members having formed thereon substantially flat annular surfaces centrally and peripherally of the members, the resilient members being disposed in alternately oppositesense with like surfaces of alternate memtbers in mutual contact to define a substantially continuous flux path from the solenoid to the ferromagnetic member.

No references cited.

JOHN F. BURNS, Primary Examiner. 

1. IN COMBINATION, ELECTRICALLY OPERATED RELAY MEANS COMPRISING A SOLENOID ENERGIZABLE TO PRODUCE A MAGNETIC FIELD, AN ARMATURE MOUNTED FOR DISPLACEMENT ALONG THE AXIS OF THE SOLENOID, A CAP MOUNTED ON AN EXTREMITY OF THE ARMATURE AND SUBJECT TO THE MAGNETIC FIELD TO MOVE RELATIVE TO THE SOLENOID, AND A PLURALITY OF DISH-SHAPED SPRING MEMBERS OF LOW MAGNETIC RELUCTANCE DISPOSED COAXIALLY WITH AND NORMAL TO THE ARMATURE AND INTERMEDIATE THE CAP AND THE SOLENOID, THE MEMBERS BEING DISPOSED IN ALTERNATELY OPPOSITE SENSES OF CONCAVITY WITH SUBSTANTIAL PORTIONS OF ADJACENT MEMBERS BEING IN MUTUAL CONTACT THEREBY TO PROVIDE A SPRING FORCE TENDING TO OPPOSE MOVEMENT OF THE ARMATURE AND CAP TOWARD THE ARMATURE. 